The present disclosure relates to fixing devices and image forming apparatuses including a fixing device.
Image forming apparatuses, such as copiers, printers, and facsimile machines, include an image forming section and a fixing device. The image forming section forms a toner image and transfers the formed toner image to paper (fixing target). Subsequently, the fixing device fixes the transferred toner image to the paper. Thus, the image is formed on the paper. A general fixing device includes a fixing roller which heats and melts a toner image to fix the toner image to paper and a pressure roller which applies pressure to paper against the fixing roller.
The adhesiveness of the melted toner may cause paper to be wound to the outer peripheral surface of the fixing roller or the pressure roller in the fixing device in some cases. To tackle this problem, there is known a fixing device which additionally includes a separation means to separate paper wound around the fixing roller or the pressure roller from the fixing roller or the pressure roller.
For example, a fixing device is known which includes, as a separation means, a separation claw in contact with a roller. The separation claw comes into contact with the lead edge of paper that has passed on the roller. This can separate the paper from the roller. Thus, the paper can be prevented from being wound around the roller.
Where the separation claw is used as a separation means, the separation claw is in contact with the roller to rub a mold release layer coated on the surface of the roller. This may wear out the mold release layer. Further, such wearing out may tend to shorten the lifetime of the roller.
To tackle this problem, a fixing device is proposed in which the position of the separation claw in contact with the surface of the roller is changed to avoid local damage of the roller (hereinafter referred to as a first fixing device).
The first fixing device can avoid local damage of the roller to delay replacement of the roller. However, even in the first fixing device, the lifetime may be shortened due to wearing out since the separation claw is in contact with the roller. Further, in the first fixing device, paper dust or toner gathered by the separation claw in contact with the roller may return to the roller to cause significant impairment of the image quality. Moreover, where the separation claw is in contact with a fixing roller, which is to be heated to high temperature, a heat resistant material must be used as a material for the separation claw, which may invite an increase in manufacturing cost.
In order to avoid the above problems, which are cased due to contact between the separation claw and the roller, a fixing device is proposed which uses a separation plate as a separation means (hereinafter referred to as a second fixing device). In the second fixing device, the separation plate is arranged so as to be out of contact with the roller. This may prevent the lifetime of the roller from being shortened and the image quality from being impaired. In turn, an increase in manufacturing cost can be suppressed.